28 
GEOLOGY OP NORTH CAROLINA. 
corner of Tancey county, gets the name from the character of its con- 
spicuous, bare, dome-like summit, which is covered with natural 
meadows like the Roan. 
Geological structure and origin of mountains. — The simplest and the 
general aud popular conception of the structure and mode of formation 
mountains is, that they are the result of a simple upward bending of 
the strata, which will therefore be found sloping upward on both sides 
towards the axis of elevation. This is in fact the structure observed in 
many instances, and no doubt most of the existing mountains are the 
result of various subsequent modifications of such an original structure ; 
but in most cases it has been entirely obliterated by denudation, that is, 
by the action of the atmosphere and the frost in disintegrating and 
breaking down the rocks, and of water in removing the debris. So that 
all the existing forms of land surface, its topographical features, the 
mountains, hills and valleys, are the result of a long continued process of 
atmospheric sculpture. The simple anticlinal structure resulting from 
the folding and flexure of the strata is not often observed. A very com- 
mon modification results from a fracture along; the crest of such an an- 
ticlinal fold, through which the atmospheric forces attack the edges of 
the softer and more disintegrable strata and scoop out a valley along the 
ridge ; and the process may go on, undermining and removing also the 
harder and more resisting materials until a wide valley is opened between 
two monoclinal ledges bounding it on either hand ; or, one or both of 
these may be entirely removed, leaving no signs of the former elevation 
except the opposite dips of the strata, or only an occasional projecting 
ridge or knob of refractory rocks ; or the deepening and grooving may 
be continued far below the original valle\ r s, so that these become the hills 
and mountains, with, of course, a synclinal structure, the strata on either 
side inclining towards each other downward. The mountains of this State 
do not present a well defined example of either the anticlinal or the syn- 
clinal structure ; they are all monoclinal / i. e ., the rocks composing them 
all have one dip, often very confused, aud generally quite steep ; they are 
simply projecting ledges of the hard and difficultly decomposable rocks, 
left by tbe erosion of tbe neighboring softer strata. 
The topographical features of the mountain region of the State above 
briefly sketched, are not accidental. There can be no doubt that here 
was once a lofty plateau higher than the highest summit of the Black, 
and comparable in elevation to the present great table land on the wes- 
tern side of the continent, between the Iiocky Mountains and the Sierra 
Nevada. The destructive action of atmospheric agents, chemical and 
mechanical, — water, frost, oxygen, carbonic acid, — have by their incessant 
